Made Up, Upstairs at Soho Theatre, London

How do you review a play that is different every night? Theatre troupe Cartoon de Salvo have been around for fifteen years offering up varying levels of improvisation in their devised works. For their latest show, Made Up, the three actors ask the audience to come up with a title and we watch them conjure a show from thin air. The play changes every day, depending on the title. When it works, the superb actors are like magicians, producing comedy, pathos and music from nowhere (I know this, having seen their 2008 hit Hard Hearted Hannah). But when it doesn’t work, as it didn’t this evening, the result is agonising.

The title our audience chose was Hunting the Shark. You might think that would lend itself to fast-paced chases and Jaws-style terror. But the opening 20-minute scene was a painful enactment of a captain on his ship with two mates. Precisely nothing happened bar some enthusiastic toking on imaginary pipes and gesturing at the rigging. The dialogue faltered, you could see the cogs in the brain of each actor working as their faces tried not to betray the desperate thought “What do I do next?” but failed.  A bit of relief came from the excellent extemporising five-piece band The Adventurists, whose percussive tapping, singing and strumming was an amusing backdrop. You could see them trying to force the main players into song during the low ebbs.

Things livened up when the lights (thankfully) went down on the boat scene and the strongest of the trio, Brian Logan, began influencing operations. He immediately added the comedic and storytelling elements sorely lacking in the opening minutes. Director and performer Alex Murdoch joined him as his hilarious monkey companion, Fidget, whose squawking monkeying around stole all attention from the plot. There were a few moments of pleasurable comedy, but things soon lapsed once more into badly pitched, staid action.

They are a talented bunch and the nature of what they do means on some nights I bet this is a five star show. However, I spent last night wondering where the story could possibly go. Great examples of theatre devised off-the-hoof in this way generally include a frenzy of creative material, usually offbeat, which provide multiple story threads for the collaborating actors to tug on and take further. This performance lacked that. It was cautious, too slow and frustrating to watch. It's a very hard task to conjure a play out of thin air every night.

Until 21 April. Box office 020 7478 0100